It's particularly enraged by my call - and that of others - for Griffin to be prosecuted.

Faced with widespread public outrage, the BNP is desperately trying to divert attention, and take the heat off Griffin, by launching a smear campaign against its main public critics, Liberty and myself.

In bid to discredit me and undermine my criticism of Griffin, the BNP website has gone even further; explicitly denouncing me as "paedophile apologist...who wants to legalise the paedophile abuse of children by abolishing the age of consent laws."

None of this is true. I have always condemned adults having sex with children and campaigned to empower young people to resist and report sex abusers. I've never argued or campaigned for the abolition of the consent laws.

I guess I should be enraged by such lies and gutter tactics. But I'm not. No one takes Griffin and the BNP seriously these days. They are sad, pathetic, desperate losers; clutching at straws to deflect attention away from their sinking reputations, declining electoral fortunes and violent in-fighting. The bigger and more outrageous their fabrications, the stronger the evidence of their lack of arguments, credibility and moral authority.

The slurs against me are actually a back-handed compliment; proof that the BNP takes me seriously and has been damaged by my criticisms - now and in years gone by. They want revenge.

But the bid to defame me has got no traction. Everyone knows that as a human rights campaigner I'd never endorse child sex abuse - or any abuse of any one for any reason. All that these far right smear tactics have done is show up the BNP as a vicious, unprincipled neo-fascist rump.

This latest saga began yesterday afternoon, when Griffin, who is a Member of the European Parliament, Tweeted:

"So Messrs Black & Morgan, [address given] A British Justice Team will come up to [address given] and give you a..."

"...bit of drama by way of reminding you that an English couple's home is their castle. Say No to heterophobia!"

Griffin claims people like me are objecting to his tweet on the grounds that it is "offensive". Wrong. More than offensive, it's sinister.

If his Tweet had been posted by the leader of the Women's Institute most of us would be surprised but not fearful. Coming from the leader of the BNP gives this tweet an altogether more scary, alarming character. BNP members have been convicted of incitements, harassment and violence. In this context, many people read Griffin's tweet as menacing.

I know from first-hand experience. In the past, BNP supporters have sent me similar messages, which were later followed up with actual physical attacks on me and my flat.

Griffin's warning to the gay couple that they will visited at their home by a "British Justice Team" and be given a "bit of drama" could be construed as implying the dispensation of justice; that the gay couple will be given the justice they deserve by the BNP's enforcers.

In response to criticism of Griffin's tweet, BNP supporters are whingeing that he is being denied free speech. I'm the first to defend freedom of speech, even the free speech of people with whom I profoundly disagree. However, Griffin's tweet is not a simple free speech issue. He seems to have crossed the line from free speech into the realm of menace, threat and intimidation.

It is an abuse of freedom of speech to use or suggest menace. This closes down debate. It makes people who feel menaced afraid to speak and participate. They are intimidated into silence, for fear of the possible consequences.

Free speech should normally only be criminalised in two circumstances. First, in the instance of damaging untruths, which harm a person's reputation or put people in physical danger, such as false allegations of tax fraud or child sex abuse. Second, in the case of threats, harassment, intimidation or incitement to violence.

In my opinion, there is sufficient evidence to prosecute Nick Griffin for a menacing tweet that is likely to cause alarm, distress and fear. Arrest him.